Which of the following is a symptom commonly associated with halitosis?

Halitosis, commonly known as bad breath, is often linked to a variety of oral health issues, and one of the key symptoms associated with it is dry mouth. When the mouth is dry, saliva production decreases, and saliva is essential for washing away food particles and bacteria that can lead to unpleasant odors. A reduced saliva flow can therefore contribute significantly to halitosis, as bacteria in the mouth thrive in dry conditions and produce foul-smelling byproducts.

The other symptoms listed, while they can occur in various oral health conditions, are not directly indicative of halitosis. For instance, swollen gums are more indicative of gum disease, a condition that may accompany halitosis but isn't a symptom of it. Similarly, a burning sensation and persistent cough can be related to other medical or environmental issues but do not specifically link to the presence of bad breath as a primary symptom. Therefore, dry mouth stands out as the most relevant symptom associated with halitosis.